1. Field of the Invention
The present invention relates to an apparatus for measuring fraction purity of a chromatogram peak in liquid chromatography or flow injection analysis.
The present invention also relates to a fraction collector for separating a sample into fractions with a liquid chromatograph thereby collecting designated fractions.
2. Description of the Background Art
In liquid chromatography or flow injection analysis, a chromatogram peak is obtained with time. Even if such a peak has a simple configuration, however, it may consist of at least two components in an inseparated state.
In order to decide whether or not a chromatogram peak as obtained consists of only a single component, employed is a specific chromatogram method, which is adapted to obtain chromatograms with two different wavelengths through an optical detector and take the ratio of the two chromatograms, thereby measuring fraction purity values of peaks. A peak which consists of a single component has a constant wavelength characteristic in every position. Therefore, the ratio of two chromatograms taken with different wavelengths remains constant in all positions. If the peaks consist of at least two components, on the other hand, wavelength characteristics of spectra are varied with positions of the peaks due to difference of component rates, whereby the ratio of the chromatograms is varied with the positions of the peaks.
When the fraction purity is measured by such a specific chromatogram method, it is possible to decide whether the as-obtained peak consists of a single component or at least two components. However, it is difficult to decide the percentage of such a possibility that the peak consists of a single component in a certain range between its start and end points. Therefore, it is difficult to decide time range for fraction collecting, for example, by the specific chromatogram method.
In order to collect fractions of a sample by liquid chromatography, employed is a method of previously setting collecting times for the target components in response to the retention times of the components, or a method of checking the order of the peaks of the target components on the chromatogram for collecting fractions appearing on the peaks of the order upon peak detection.
In the method responsive to the retention times, the fractions may be erroneously collected in positions displaced from the peaks of the target components since the retention time of each component is varied with slight difference of temperatures or mobile phases, or difference between injection volumes of the sample. In the method responsive to the peak order, on the other hand, the order may be upset by contamination of an unexpected impurity such that other components are erroneously collected. Thus, it is difficult to correctly collect fractions by the conventional method.